• Child Health Nursing Research
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• 제12권2호
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• pp.196-203
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• 2006

Objectives: This study was conducted to test whether stretching helps high school students recover from their fatigue and improve concentration. Method: The method of this study adopted a nonequivalent control group with pre-test and post-test designs. The period of data collection was from November to December in 2004. The 135 subjects were randomly selected from two high schools in Ulsan : one school as control group(n=66) and the other school as an experimental group(n=69). The experimental group had stretching for 10 minutes before the start of their fifth period class, five times a week(once a day) 4weeks of period, but the control group did not do. Result: After stretching, the students' level of fatigue in the experiment group was immensely reduced (t=4.75, p<.001). After the stretching, the concentration level of the experimental group increased vastly compared to the control group (t=3.35, p≤.005). Conclusion: Stretching is useful to reduce fatigue and improve concentration of high school students. This study recommended that stretching, which is not limited by high physical techniques, or specific time or spaces would help high school students' health, since they do not exercise regularly and are tired physically and mentally.

• Asian Journal of Atmospheric Environment
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• 제8권4호
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• pp.192-201
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• 2014

A comprehensive profile of volatile organic compounds (VOCs) in public spaces is needed for interpreting indoor air measurements. Seasonal differences in profiles are critical for epidemiological study and risk assessment. The purposes of this study were to establish profiles for individual VOCs in 50 indoor public places in Korea and to determine seasonal variations in their concentrations. Air samples were taken during working hours. Seventy-two of the 91 targeted VOCs were identified using multiple standards. Six VOCs detected in all summer and winter samples were toluene, acetone, m,p-xylenes, ethylbenzene, benzene, and styrene. In summer, methyl ethyl ketone and 1-butanol were also found in all samples. In both seasons, the dominant indoor VOCs were toluene, m,p-xylenes, ethylbenzene, acetone, and isopropyl alcohol. Other chemicals associated with gasoline emissions were dominant in summer. Limonene was dominant only in winter due to the consumption of tangerines. The nine VOCs with the highest concentrations comprised 64.8% and 49.6% of the TVOC in summer and winter, respectively. Comparing two types of adsorbent tube, a single adsorbent tube with Tenax-TA had similar detection performance as a double adsorbent tube with Tenax and Carbotrap.

• Journal of Periodontal and Implant Science
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• 제35권3호
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• pp.777-788
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• 2005

The primary stability of implants is an important factor to predict the osseointegration. Recently, the resonance frequency analysis has been used to measure the primary stability. It is an objective method to monitor the stability of implants during healing phase. This study is to validate the differences in the effect of the osteotome method according to the bone quality as well the thickness of cortical bone. Two hundred seventy implants of 3.75mm in diameter(Neoplant, Neobiotech, Korea) were placed in 135 bovine ribs. The bone quality is classified into 3 classes according to the number of bone marrow spaces which implants would be placed, and then classified into 9 subclasses after the ribs were trimmed. Two implants were placed in 15 specimens of each class. The conclusion were as follows: 1. In case of less dense cancellous bone, the oseotome method is more effective in primary stability rather than the drilling method(p <0.05). 2. If there was cortical bone, it is more advantagous to get stronger primary stability. 3. If cancellous bone is more dense or if cortical bone exists, there is no statistical significance between drilling and osteotome method(p <0.05).

• Kyungpook Mathematical Journal
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• 제46권4호
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• pp.503-507
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• 2006

Let X be a Tychonoff space and ${\sum}(X)$ the set of all the subrings of C(X) that contain $C^*(X)$. For any A(X) in ${\sum}(X)$ suppose $_{{\upsilon}A}X$ is the largest subspace of ${\beta}X$ containing X to which each function in A(X) can be extended continuously. Let us write A(X) ~ B(X) if and only if $_{{\upsilon}A}X=_{{\upsilon}B}X$, thereby defining an equivalence relation on ${\sum}(X)$. We have shown that an A(X) in ${\sum}(X)$ is isomorphic to C(Y ) for some space Y if and only if A(X) is the largest member of its equivalence class if and only if there exists a subspace T of ${\beta}X$ with the property that A(X)={$f{\in}C(X):f^*(p)$ is real for each $p$ in T}, $f^*$ being the unique continuous extension of $f$ in C(X) from ${\beta}X$ to $\mathbb{R}^*$, the one point compactification of $\mathbb{R}$. As a consequence it follows that if X is a realcompact space in which every $C^*$-embedded subset is closed, then C(X) is never isomorphic to any A(X) in ${\sum}(X)$ without being equal to it.

• 한국실내디자인학회:학술대회논문집
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• 한국실내디자인학회 2007년도 추계학술발표대회 논문집
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• pp.216-219
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• 2007

New paradigm of modern society today - environmentally sound and sustainable development - led to the attempt on the introduction of natural elements in various spaces by people's interest in the quality of life. As one of the distinguished space marketing in designing the outer space of resort, this plan attempts to limit artificial boundary within open scenery, thus creating nature within nature - interior theme garden. In addition, this plan is aimed to obtain location property of inner garden through limited boundary, to promote the identity of resort by endowing it with new values in space and to form emotion care garden and culture garden for users. The plan has proceeded under the following concepts. 1) Differentiation from outer space has been made by creating a theme garden with unique theme garden - landscape elements and an attempt have been made to increase the values of interior garden through the introduction of new species of plants and the state-of-the-art facilities. 2) Emotion care garden - The garden has been created to get emotion purified systematically within nature and let people take a rest and enjoy their spare time. 3) Culture garden - The garden has been planned where culture could be created through various experience activities as a space with education and entertainment by providing a variety of interesting elements.

• Geomechanics and Engineering
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• 제37권2호
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• pp.149-166
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• 2024

The acoustic emission (AE) technique is utilized to estimate the rock failure status in underground spaces. Understanding the AE characteristics under loading conditions is essential to ensure the reliability of AE monitoring. The AE characteristics depend on the material properties (p-wave velocity, density, UCS, and Young's modulus) and damage stages (stress ratio) of the target rock mass. In this study, two groups of granite specimens (based on the p-wave velocity regime) were prepared to explore the effect of material properties on AE characteristics. Uniaxial compressive loading tests with an AE measurement system were performed to investigate the effect of the rock properties using AE indices (count index, energy index, and amplitude index). The test results were analyzed according to three damage stages classified by the stress ratio of the specimens. Count index was determined to be the most suitable AE index for evaluating rock mass stability.

• Journal of Mechanical Science and Technology
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• 제16권8호
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• pp.1144-1153
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• 2002

A hybrid performance prediction method is proposed in the present study. A channel diffuser is divided into four subregions: vaneless space, semi-vaneless space, channel, and channel exit region. One-dimensional compressible core flow and boundary layer calculation of each region with an incidence loss model and empirical correlation of residuary pressure recovery coefficient of a channel predict the performance of diffusers. Three channel diffusers are designed and tested for validating the developed prediction method. The pressure distributions from an impeller exit to the channel diffuser exit are measured and discussed for various operating conditions from choke to nearly surge conditions. The strong non-uniform pressure distribution which is caused by impeller-diffuser interaction is obtained over the vaneless and semi-vaneless spaces. The predicted performance shows good agreement with the measured performance of diffusers at a design condition as well as at off-design conditions.

• 대한수학회지
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• 제52권3호
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• pp.625-636
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• 2015

The Boolean rank of a nonzero $m{\times}n$ Boolean matrix A is the least integer k such that there are an $m{\times}k$ Boolean matrix B and a $k{\times}n$ Boolean matrix C with A = BC. We investigate the structure of linear transformations T : $\mathbb{M}_{m,n}{\rightarrow}\mathbb{M}_{p,q}$ which preserve Boolean rank. We also show that if a linear transformation preserves the set of Boolean rank 1 matrices and the set of Boolean rank k matrices for any k, $2{\leq}k{\leq}$ min{m, n} (or if T strongly preserves the set of Boolean rank 1 matrices), then T preserves all Boolean ranks.

• 한국수학사학회지
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• 제28권3호
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• pp.133-149
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• 2015

Arrivals of Hilbert and Minkowski at $G\ddot{o}ttingen$ put mathematical science there in full flourish. They further extended its strong mathematical tradition of Gauss and Riemann. Though Riemann envisioned Finsler metric and gave an example of it in his inaugural lecture of 1854, Finsler geometry was officially named after Minkowski's academic grandson Finsler. His tool to generalize Riemannian geometry was the calculus of variations of which his advisor $Carath\acute{e}odory$ was a master. Another $G\ddot{o}ttingen$ graduate Busemann regraded Finsler geometry as a special case of geometry of metric spaces. He was a student of Courant who was a student of Hilbert. These figures all at $G\ddot{o}ttingen$ created and developed Finsler geometry in its early stages. In this paper, we investigate history of works on Finsler geometry contributed by these frontiers.

• Journal of applied mathematics & informatics
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• 제8권1호
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• pp.59-69
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• 2001

The paper deals with the interaction between three Griffith cracks propagating under antiplane shear stress at the interface of two dissimilar infinite elastic half-spaces. The Fourier transform technique is used to reduce the elastodynamic problem to the solution of a set of integral equations which has been solved by using the finite Hilbert transform technique and Cooke’s result. The analytical expressions for the stress intensity factors at the crack tips are obtained. Numerical values of the interaction efect have been computed for and results show that interaction effects are either shielding or amplification depending on the location of each crack with respect to other and crack tip spacing. AMS Mathematics Subject Classification : 73M25.